Homopolar linear synchronous machine utilizing a cold plate

ABSTRACT

Disclosed is a yoke-less mover of a homopolar linear synchronous machine. The yoke-less mover may include a cold plate having slots. Ferromagnetic cores are fixed to the cold plate. Each of the ferromagnetic cores may protrude through a respective one of the slots, creating gaps between the ferromagnetic cores. Armature windings are fixed to the cold plate. The armature windings may occupy the gaps between the ferromagnetic cores. The ferromagnetic cores of the yoke-less mover have better ferromagnetic utilization and lower weight. It also enables more flexible topologies in the armature windings.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority and benefit of U.S. ProvisionalApplication No. 62/733,551 filed on Sep. 19, 2018, the disclosure ofwhich is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to the field of electric motors,particularly a homopolar machine for use in linear propulsion systems.

BACKGROUND

A direct drive motor is a type of synchronous motor that directly drivesthe load, rather than using a transmission or gear box. Linear motorsare generally direct drive motors as it is generally not feasible tohave any intermediary components. As applications for large scale linearmotion increases, direct drive motors have been increasingly explored.The constraints of a high-speed, high-power transportation system imposechallenges that are not present in the state of the art. This isespecially true in environmentally controlled and evacuatedenvironments, where aero drag no longer constitutes the vast majority ofdrag present in the system. Instead, the new challenges faced arerelated to electromagnetic drag due to iron losses, mass efficiency,electrical efficiency, and thermal management. In a transportationsystem that seeks to promote high-speed, high-efficiency, and high-powerdensity, a novel employment of a homopolar linear synchronous machineoffers vast improvements in the state-of-the-art.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this disclosure will be best understood byreference to the following detailed description of embodiment, taken inconjunction with the accompanying drawings, in which:

FIG. 1 shows a perspective view of an exemplary embodiment of amover/rotor that can serve as a moving member of a homopolar linearsynchronous machine.

FIG. 2 shows a perspective view of a substantially flat rectangularshape of a cold plate with cold plate faces on opposite sides of thecold plate and armature windings of a motor in accordance with oneembodiment.

FIG. 3 shows armature windings with a flat surface that mates with acold plate in accordance with one embodiment.

FIG. 4 shows a perspective view of a cold plate with core mounting holesand eddy current slits in accordance with one embodiment.

FIG. 5 shows a top view of a cold plate with slots for mounting cores,eddy current slits, and cooling channels in accordance with oneembodiment.

FIG. 6 shows a perspective view of a base plate and a top plate of acold plate in accordance with one embodiment.

FIG. 7 shows a plot of the power loss in the cold plate for one polepair due to eddy current for resistivity properties of differentmaterials of the cold plate in accordance with one embodiment.

FIG. 8 shows mounting brackets used to affix cores to a cold platethrough core mounting holes so that the cores protrude through slots inthe cold plate in accordance with one embodiment.

FIG. 9 shows a mover that incorporates one or more cooling ribbons forfield windings of a motor on a cold plate in accordance with oneembodiment.

FIG. 10 shows a cross-sectional view of a yoke-less mover with armaturewindings in the longitudinal x-direction (e.g., direction of movement ofthe mover) and in the vertical z-direction in accordance with oneembodiment.

FIG. 11 shows the flow of magnetic flux through the cores and throughair gaps between a yoke-less mover and a track in accordance with oneembodiment.

FIG. 12 shows a cross-sectional view of fractional slot concentratedwindings (FSCW) in the longitudinal x-direction and in the verticalz-direction of a yoke-less mover as one example topology of armaturewindings of a yoke-less mover in accordance with one embodiment.

FIG. 13 shows a perspective view of the FSCW of the armature windingsand cores of a yoke-less mover in accordance with one embodiment.

FIG. 14 shows a cross-sectional view of a 6-layer integer winding (IW)in the longitudinal x-direction and in the vertical z-direction of ayoke-less mover as one example topology of armature windings of ayoke-less mover in accordance with one embodiment.

FIG. 15 shows a perspective view of the IW of the armature windings andcores of a yoke-less mover in accordance with one embodiment.

FIG. 16 shows a cross-sectional view of stepped armature windings in thelongitudinal x-direction and in the vertical z-direction of a yoke-lessmover as one example topology of armature windings of a yoke-less moverin accordance with one embodiment.

DETAILED DESCRIPTION

The features which are characteristic of the disclosure, both as tostructure and method of operation thereof, together with further objectsand advantages thereof, will be understood from the followingdescription, considered in connection with the accompanying drawings. Itis to be expressly understood, however, that the drawings are for thepurpose of illustration and description only, and they are not intendedas a definition of the limits of the disclosure.

The present embodiment relates to a system with a moveable rotor and arelatively fixed stator such that the two together form a homopolarlinear synchronous machine. The rotor may include an at least one coilwinding, an at least one core, and an at least one cold plate. A coremay be constructed from a ferromagnetic material, such as silicon steel.A core may be laminated, such that the core is constructed from at leasttwo sheets of metal that have been joined together. The lamination ofthe core may be grain oriented and non-grain oriented. A cold plate mayinclude a rectangular sheet of aluminum. The cold plate may have coolingchannels for removing heat. The cold plate may also serve as the mainstructural unit of the rotor. The cold plate may have substantiallyparallel hollow slots removed from the cold plate. The hollow slots maybe rectangular in shape. The core may be joined to the cold plate, suchthat the core fits substantially within a hollow slot of the cold plateand the core may be substantially connected to the cold plate by any ofknown means, such as mounting brackets. A portion of the core may extendbeyond at least one face of the cold plate, such that when viewed downthe length of the cold plate, the core may be visible extending out fromat least one side.

A plurality of cores may be joined to the cold plate. In an embodiment,a second core may be attached to a cold plate in a location that isoffset from a first core, such that the second core and the first coreare substantially parallel. The at least one coil winding may include anarmature winding and a field winding, either alone or paired together.The winding may be made from a conductive material, such as anodizedaluminum foil. In an embodiment, the rotor may include a field windingthat is oriented such that the winding is substantially entirely alongthe outer perimeter of a face of the cold plate. In an embodiment, therotor may include an at least one armature winding, wherein the loopformed by the winding has a face that is oriented substantially parallelto a face of the cold plate. The armature winding may be locatedsubstantially on an outer face of the core. In an embodiment, thearmature winding may include an at least one armature coil. Anembodiment may include a rotor with several armature coils on the lengthof the rotor, wherein each armature coil may represent an electricalphase of multi-phase electrical power.

A core may be located such that it is substantially between a firstarmature coil and a second armature coil. The armature winding may besubstantially enclosed by the field winding, such that the armaturewinding has a face that is adjacent to a face of the cold plate, withinthe bounds of the field winding. The field winding may be secured to thecold plate by any of known means, such as stainless steel straps andPTFE brackets.

The stator may include an at least one c-channel segment made of aferromagnetic material, such as silicon steel. In an embodiment, thec-channel segment may be laminated such that the c-channel segment isconstructed from at least two sheets of metal that have been joinedtogether. In an embodiment, the c-channel segment may be substantially“C” shaped, such that the rotor may be able to pass through the centerhollow portion of the “C”. The stator may include two or more offsetc-channel segments, such that there is a gap between each c-channelsegment, and the channel segments are arranged substantially with thehollow section of each c-channel segment forming a substantiallycontinuous path for a rotor to move through. The stator may besubstantially fixed relative to the rotor.

At least one ripple spring may be used to press the armature windingsagainst the cold plate. In an embodiment, the end windings are incontact with the cold plate to maximize surface area of windings thatare exposed to the cold plate. The armature windings may be configuredas fractional slot concentrated windings, with alternating windingsdistributed throughout the ferromagnetic core located along a length ofthe rotor.

In one embodiment, the armature coils when viewed from cross-section maybe arranged in layers, such that all armature coils of the same phasemay be the same distance from a core face, and armature coils ofdifferent phases may be different distances from a core face. A portionof a first armature coil in a first layer may overlap a portion of asecond armature coil that is in a second layer. Such an embodiment mayhave a short pole pitch as a result.

The propulsion of the rotor along a stator track may incorporatewireless charging. The use of electromagnetic fields allows for an easytransition into inductor-based charging, allowing a vehicle or otherbattery to charge as the rotor moves along the stator. In an embodiment,charging may be accomplished by having windings located on the track.

The distinct coil windings may be powered by multiple power sources,such as low power drives, rather than a conventional high power drivesupplying power to an entire propulsion system. Each low power drive maybe connected to one or more pole pairs.

In one embodiment, the cold plate may be laminated to reduce eddycurrents.

The cold plate may take on a design such as a “teethed” geometry, withgaps across the cold plate. The cold plate may be made of a coolingmetal with favorable thermal properties such as aluminum, magnesium, andstainless steel. The armature coils and field coils may be substantiallyin contact with the cold plate, such that heat is transferred out of thearmature coils and field coils and into the cold plate. In anembodiment, the cold plate may have an at least one cooling channel on aface. Cooling channels may be removed from a block, such as through gundrilling, and designed into adjoining faces of separate plates that aresubstantially attached, such as through vacuum brazing.

A high speed transportation system may include a homopolar linearsynchronous machine. The rotor may be substantially attached to apayload, such as by including bolt holes in the cold plate that may beconnected to the payload. The payload may be a vehicle, such as forcargo and passengers. An embodiment can use conductive shielding on therotor to avoid plasma generation. The rotor may be attached to thepayload in any of one or more orientations, such as on the top, bottom,and side of the payload, so long as a corresponding stator segment issubstantially connected to a surface in an orientation that allows therotor to pass through a channel segment in the direction of motion. Thestator may be attached to a fixed surface, such as the inside of a tube.The stator may be substantially fixed in any orientation, so long as therotor has a substantially matching orientation to allow the rotor topass through the channel segment. In an embodiment, the high speedtransportation system may be enclosed such that the travelling path maybe partially evacuated.

An embodiment is directed toward a process for using the homopolarlinear synchronous machine as a propulsion system for a high-speedtransport system in a low-pressure environment. The rotor may besubstantially attached to a payload, such as by including bolt holes inthe cold plate that may be connected to the payload. The payload may bea vehicle, such as for cargo and passengers. An embodiment can useconductive shielding on the rotor to avoid plasma generation. The rotormay be attached to the payload in any of one or more orientations, suchas on the top, bottom, and side of the payload, so long as acorresponding stator segment is substantially connected to a surface inan orientation that allows the rotor to pass through a channel segmentin the direction of motion. The stator may be attached to a fixedsurface, such as the inside of a tube. The stator may be substantiallyfixed in any orientation, so long as the rotor has a substantiallymatching orientation to allow the rotor to pass through the channelsegment. Power may be passed to the windings on the rotor, introducing amagnetomotive force. The varying magnetic flux comes from the saliencyof the channel segments relative to the field winding, introducing afield flux path that closes substantially perpendicular to the directionof motion. Thrust may be generated by the interaction between the fieldflux and the current in the armature coils.

As described, the cold plate serves multiple purposes, for example,absorbing thermal energy from field coils, armature coils, andferromagnetic cores, while also serving as the main or primarystructural member of the rotor/mover. In one embodiment, FIG. 1 shows amover/rotor 150 that can serve as a moving member of a homopolar linearsynchronous machine. The mover includes a cold plate 152 having one ormore cooling channels formed within the cold plate (see, for example,cooling channel 172 and 192 of FIG. 6). A plurality of armature windings156 are fixed to the cold plate. Similarly, one or more field windings158 are fixed to the cold plate. Although the opposite face of the coldplate is not visible in FIG. 1, it should be understood that theopposite face can also have the same configuration, e.g., cores 154,armature windings 156, and field windings 158. The cores 154 passthrough slots of the cold plate, thus each core is shared between bothfaces. The bottom face of the cooling plate (not shown), however, canhave additional armature windings and field windings attached. Thus, itshould be understood that the features mentioned for one of the fieldwinding and armature windings on one face of the cold plate can also beapplicable to the field winding and armature windings on the opposingface of the cold plate.

In one embodiment, a plurality of ferromagnetic cores 154 are fixed tothe cold plate, each ferromagnetic core positioned within a loop orboundary formed from at least one of the plurality of armature windings.Similarly, the plurality of armature windings and the plurality offerromagnetic cores can be fixed to the cold plate within the outerperimeter of the cold plate, e.g., within boundary formed by fieldwinding 158. Each field winding can be oriented substantially along anouter perimeter (see, for example, outer perimeter 180 shown in FIG. 5)of a face of the cold plate, secured by known means such as a strap,PTFE bracket, or other combination of connecting and fastening members.

The cold plate serves as the primary structural member of the mover, forexample, by providing sufficient strength and stiffness, to maintain thepositions and orientations of the armature windings, field windings, andcores. Such structure is especially needed, for example, when the movingmember is propelled by magnetic force generated by the armature windingsand the one or more field windings, when electrical current passesthrough them. The cold plate can be a single structure that the othercomponents (the coils and the cores) can affix/mount to. In oneembodiment, no additional structural members, other than the coolingplate, are connected between the plurality of armature windings, theplurality of ferromagnetic cores, and the one or more field windings. Inone embodiment, the mover has only a single cold plate. Although onepayload may attach to a plurality of movers, each mover can have asingle cold plate onto which the core and windings are attached.

As described, the components are fixed to the core at designatedpositions and orientations. The body of the cold plate is sufficientlystiff, strong, and durable to maintain relative positions andorientations of each component while simultaneously absorbing thermalenergy from the components. Such positions and orientations are candetermine alignment of magnetic fields generated by the windings. Thosemagnetic fields, in turn, generate the propulsion force of the machineand propel the mover (e.g., through the stator). Thus, it is criticalthat the positions and orientations of the components be maintainedunder different load conditions.

The cold plate synergistically provides both cooling and structuralintegrity. This feature saves on design cost and reducescomplexity—additional structural parts, such as skeleton brackets,housings, etc., can be reduced and/or obviated. Further, a separatecooling structure does not have to be developed because the cooling isintegrated as the primary structural element onto which the coils andcores are affixed to. Referring to FIG. 2, the cold plate 152 can have asubstantially flat rectangular shape with a first cold plate face 162and a second cold plate face 164 on the opposite side of the first coldplate. It should be understood that FIG. 2 does not show the fieldwindings to provide a less obstructed view of the cores and armaturewindings and cold plate. In one embodiment, the armature windings andone field winding are mounted to each surface, e.g., one field windingcan be mounted to the first face 162 while a second field winding ismounted to the second face 164.

In one embodiment, the plurality of armature coils and the one or morefield windings each have at least one flat section that is in contactwith the cold plate. For example, referring to FIG. 1, an underside offield winding 158 that is in contact with cold plate 152, although notvisible in the drawing, can be flat. The flat surface of the windingscan provide sufficient surface area allowing transfer of thermal energyfrom the field winding to the cold plate. Similarly, as shown in FIG. 3,the armature winding can have a flat surface 157 that mates with thecold plate 152.

The payload (e.g., a vehicle) can be attached to the cold plate.Referring to FIG. 8, the cold plate can have bolt holes 192 such that afastener (e.g., a bolt) can connect the cold plate (and consequently,the rest of the mover) to the payload. It should be understood that anycombination of connecting hardware such as bolts, brackets, hooks,clamps, etc., can be used to fasten the payload to the cold plate,including fastening hardware that does not require holes. Once attached,as magnetic forces propel the mover through the stator, the connectedpayload is also propelled. Thus, the cold plate further serves as theprimary structural member that transfers mechanical force from themoving member to the payload. This further reduces complexity and riskof failing parts by simplifying the transfer of force (through a singleplate) while reducing the need for additional structural and connectingmembers. Manufacturing and assembly of the machine is also stream lined.

As discussed, the cold plate can have slots and each core can fit in arespective slot. These slots can be rectangular in shape. For example,FIG. 5 shows slots 166, each having a rectangular shape, and each beingparallel to each other. In one embodiment, the slots can be sized andshaped to house the ferromagnetic cores. Thus, the cross-sectional shapeand size of the ferromagnetic cores are similar to (but slightly smallerthan) the shape of the slots. Each core can be arranged within arespective slot of the cold plate, and fixed into position. In oneembodiment, each of the cores can be aligned parallel to each other.FIG. 8 shows mounting brackets 190 can be fixed to each core 154 (e.g.,by known fastening means such as gluing, bolts, screws, etc.). Themounting brackets can mount to holes in the cold plate (e.g., coremounting holes 165 as shown in FIG. 4) thereby attaching the core to thecold plate.

The cold plate can be formed from a material (e.g., a metal) withfavorable thermal conductivity properties. It is appreciated, however,that eddy currents develop at the cold plate due to the magnetic fieldsgenerated by the coils. Eddy currents can cause resistive losses. Thus,the resistance of the cold plate material is also a consideration, sincehigher electrical resistance lowers eddy currents. In one embodiment,the cold plate can include or be formed from aluminum, magnesium,stainless steel, titanium, or another material with suitable thermalconductivity and electrical resistance. In one embodiment, the coldplate can be formed entirely from 304 stainless steel, to minimizeelectrical conductivity while maintaining sufficient thermalconductivity. Referring now to FIG. 7, although stainless steel does nothave the highest thermal conductivity, the resistivity there issufficiently high to reduce cold plate loss to approximately 800 Wattsper pole pair. Cold plates formed from materials such as copper,aluminum, and magnesium have been shown to result in higher losses.

In one embodiment, the cold plate has a substantially flat shape.Referring to FIG. 4, in one embodiment, the plate has a flat rectangularshape. Although the shape can vary, the flat rectangular shape can beused so that the mover can fit within and move through the c-channelsegments of the stator. It should be understood that dimensions of thecold plate and mover can vary based on application (e.g., size ofintended payload, max intended speed, etc.).

Referring to FIG. 5, the cold plate can have one or more coolingchannels 172 formed within the cooling plate. Coolant (e.g., water orother known fluid) can be circulated through the cooling plate to absorbthermal energy. In this manner, thermal energy is transferred from thecoils and core affixed to the cooling plate, to the cooling plate, andthen to the coolant, to suppress temperatures of the machine fromreaching inoperable conditions, resulting in performance degradationand/or equipment damage. Each of the one or more cooling channels canhave at least one inlet 174 and one at least outlet 174 where thecoolant can be circulated from one or more known circulation means(e.g., a pump). A chiller and/or pump can be integrated as part of themachine, or separate (e.g., attached to the payload). The chiller can beused to cool the coolant while the pump can be used to circulate thecoolant, which can be water or other known coolant. The chiller can useknown refrigeration systems.

In one embodiment, the cooling channel can have a zig-zagging back andforth pattern, traveling from a first edge of the cold plate towards asecond edge of the cold plate, then back towards the first edge, and soon, located near and/or beneath regions where the coils and the coresare located. In one embodiment, the one or more cooling channels form aloop around at least three sides of each of the rectangular slots, asshown FIG. 5. In this manner, coolant in the cooling channel can absorbthermal energy from the core and armature windings positioned at theslot.

As mentioned, the cold plate can have slits 168 formed in the coldplate. For example, as shown in FIG. 5, a slit 168 can be formed from anedge of the cold plate to each slot 166. Each slit can cut through fromone face of the cold plate to the other face of the cold plate forming apaddle portion 170 between each slot and the edge. This can reduce eddycurrents of the cooling plate, by restricting potential eddy currentpaths. In such a case, cooling channels can run up a first side of theslot, around the top of the slot, then back down a second side of theslot (forming a loop around the slot), then loop around the paddlesection 170, and then continue to a first side of an adjacent slot, andso on, until the slots (e.g., all the slots) have surrounding coolingchannels and all the paddle sections have cooling channels that runthrough them. The cooling channels in the paddle sections can helpabsorb heat from the core, and armature windings, as well as the fieldwinding, which, in one embodiment, rests on the outer perimeter of thecold plate.

In one embodiment, a process for manufacturing a homopolar linearsynchronous machine having a primary structural member on which one ormore field windings and one or more armature windings are affixed to, isdescribed. Referring to FIG. 6, the process can include forming a baseplate 194 and a top plate 193, each having a flat rectangular cubeshape. In one embodiment, the one or more cooling channels 192 areformed in the base plate, for example, through machining grooved pathson a surface of the base plate to form the channels).

In one embodiment, flatten annealing can be applied to the plates toreduce warping and improve braze quality. The base plate and the topplate can be brazed together (e.g., through vacuum brazing), thusforming a single cold plate with internal cooling channels. Referring toFIG. 5, the eddy current slits 168 and the slots 166 can be machinedfrom the top and base plates prior to brazing the plates together orafter the plates are brazed together. Similarly, other details such asholes or grooves can be machined into the cold plate either before orafter brazing.

In one embodiment, the process can include stress relieving the plates,prior to or after brazing, to minimize warping during machining, e.g.,heat treating the steel to a temperature below a critical threshold torelieve residual stress that could result from cutting, rolling, orshearing of the steel.

In one embodiment, the process includes fixing a plurality of cores, aplurality of armature windings, and one or more field windings to thecold plate, as described in other sections.

FIG. 9 shows a mover that incorporates one or more cooling ribbons,according to one embodiment. A cooling ribbon 194 can have internalchannels for circulating coolant. The ribbon can connect and attach to alength of the field winding to further absorb thermal energy from thefield winding (in addition to the cold plate). For example, the coolingribbon can connect and attach to an outer surface 196. Additionally, oralternatively, another cooling ribbon can connect and attach to an innersurface 198 of the field winding.

As discussed, the cores of the rotor may be fixed to the cold plate sothe cores, also referred to as teeth, protrude through the slots in thecold plate, as shown in FIG. 8. The cores provide the paths throughwhich the magnetic flux of the armature windings and the field windingsmay flow. Because the mover on which the rotor is situated does not needto provide axial flux paths (e.g., in the longitudinal x-directionthrough the mover), the mover may optimize for flux paths in thevertical direction (e.g., in the z-direction through the air gap of thetrack). The slots that are cut through the mover and the cold plate, andthe parallel cores protruding through the slots provide one embodimentof a yoke-less mover. Compared to a conventional yoke that provides acontinuous axial flux path, the yoke-less mover has better ferromagneticutilization and lower weight. It also enables more flexible topologiesin the armature windings. In one embodiment, the active weight of theiron and copper of the mover may be reduced by 25% while maintaining thesame thrust.

FIG. 10 shows a cross-sectional view of a mover in the longitudinalx-direction (e.g., direction of movement of the mover) and in thevertical z-direction. The mover has parallel cores 154 protruding in thez-direction on both sides of the cold plate 152 through their respectiveslots in the cold plate 152. A core does not run continuously in thelongitudinal x-direction on either surface of the cold plate 152.Instead, gaps 202 are created in the mover in the spacing between thecores 154. The gaps 202 between the cores 154 provide the space for thearmature winding. In one embodiment of the topology of the armaturewindings 156, each phase of the three-phase armature windings occupiesconsecutive gaps 202. A coil of an armature winding may thus occupy gaps202 that are separated by three cores 154 on either side of the coldplate 152. The distance between the coils of the armature windings 156of each phase extending in the x-direction may be referred to as thepole pitch. The mover may slice through the gap in the c-channel track200 along the x-direction. Magnetic flux generated by the pole pair ofthe armature winding 156 may flow through the cores 154 and an air gap204 between the mover and the c-channel track 200. In one embodiment,the air gap 204 may be 15 mm. The c-channel track 200 may be referred toas a slot, and the width of the c-channel track 200 may be referred toas the slot width. FIG. 10 shows one embodiment of a motor in which thepole pitch is twice the slot width. Other ratios of the pole pitch andslot width are possible.

FIG. 11 shows the flow of the magnetic flux 152 through the cores 154and the air gap 204. Because the teeth of the cores 154 optimize theflow of the magnetic flux in the z-direction, the magnetic flux densitythrough the cores are higher compared to a conventional yoke rotor,enabling better ferromagnetic utilization while reducing the weight ofthe mover.

In one embodiment, the cores 154 may be constructed from a ferromagneticmaterial, such as silicon steel. The cores 154 may be laminated, forexample, using M19 silicon steel laminated with C5 coating forlamination insulation. To manufacture the laminated cores, a stamplamination process may be used to bond the silicon steel into bondedlamination stacks of the motor teeth. In one embodiment, cobalt iron maybe used instead of silicon steel to improve the force output orefficiency.

The cores 154, also called motor teeth, of the yoke-less mover, mayaccommodate various topologies of the armature windings of the rotor.FIG. 12 shows a cross-sectional view of fractional slot concentratedwindings (FSCW) in the longitudinal x-direction and in the verticalz-direction. The cold plate is not shown, but it is understood that thecores 154 may protrude through their respective slots in the cold plateand the mover. The coil of a phase of the armature windings 156 may bewound around each of the cores 154 to create a pole. The three phases ofthe armature windings 156 may be positioned in three consecutive cores154 and the pattern repeated along the cores 154 of the motor in thex-direction. In one embodiment, there may be 25 cores 154 on a motor toaccommodate 24 coils of the armature windings 156 on each side of thecold plate. The 24 armature coils may be divided into four pole pairs.The 6 armature coils of each pole pair may include a pair of armaturecoils for each pole pair for each of the three phases. The FSCW may becalled as such because the pole pitch of the armature windings 156 isless than or a fraction of the width of the c-channel track 200 or theslot width. FIG. 12 shows one embodiment of the FSCW in which the polepitch is 0.5 of the slot width. FIG. 13 shows a perspective view of theFSCW of the armature windings 156 and the cores 154 from above the motoralong the x-direction.

The advantages of the FSCW in rotating motors as well as linear motorsare relatively high power density, high efficiency, short end windings,good flux weakening capability, and easier manufacturability.Additionally, for homologous linear synchronous motors, FSCW allow fortighter packaging because the FSCW do not extend beyond the DC coil ofthe field windings and also allow for easier cooling of the endwindings. However, there may be higher track losses and eddy currentloses, and high harmonic content in back electromotive force as well asair gap flux density.

In another topology of the armature windings of the rotor provided bythe cores 154 of the yoke-less mover, FIG. 14 shows a cross-sectionalview of a 6-layer integer winding (IW) in the longitudinal x-directionand in the vertical z-direction. The coil of a phase of the armaturewindings 156 may be wound around two the cores 154 separated by a gap202 to create a pole. The three phases of the armature windings 156 maybe stacked on six layers in the z-direction of the rotor such that allarmature coils of the same phase may be the same distance from a coreface, and armature coils of different phases may be different distancesfrom a core face. For example, armature coils denoted by phase A/A′ arestacked on the two outermost layers of the cores 154 on either side ofthe cold plate 152; armature coils denoted by phase C/C′ are stacked onthe two inner layers next to the A/A′ layers; and armature coils denotedby phase B/B′ are stacked on the two innermost layers. The three phasesof the armature windings 156 are also staggered so that a portion of thearmature coils of phase A/A′ in the outermost layers may overlap aportion of the armature coils of phase C/C′ in the next layer and mayalso overlap a portion of the armature coils of phase B/B′ in theinnermost layers. The pattern of the staggered armature windings 156 forthe three phases may be repeated along the cores 154 of the motor in thex-direction. FIG. 14 shows one embodiment of the IW in which the polepitch is ⅔ of the slot width. FIG. 15 shows a perspective view of the IWof the armature windings 156 and the cores 154 from above the motoralong the x-direction.

The advantages of the short-pitched 3-layer IW are lower track losses,lower asymmetry in AC inductance, less leakage flux, higher powerfactor, lower losses in cold plate, and lower force ripple. The shortend windings also allow for tighter packaging, low losses, and easiercooling.

In another topology of the armature windings of the rotor provided bythe cores 154 of the yoke-less mover, FIG. 16 shows a cross-sectionalview of stepped armature windings in the longitudinal x-direction and inthe vertical z-direction. The coil of a phase of the armature windings156 may be wound around two the cores 154 separated by a gap 202 tocreate a pole. Similar to the 6-layer IW, the three phases of thearmature windings 156 may be staggered so that a portion of the armaturecoils of phase A may overlap a portion of the armature coils of phase Band phase C. However, unlike the 6-layer IW in which the three phases ofthe armature windings 156 may be stacked to occupy respectivelydifferent layers, the three phases of the armature windings 156 allstart on the same layer but are stepped to go down to successivedifferent layers. For example, the armature windings 156 of each phasemay traverse the gap 202 between the cores 154 transversally in they-direction of the rotor along the outermost layer. The armaturewindings 156 may step down from the outermost layer to successive lowerlayers at for each successive gap 202. When the armature windings 156reach the lowest layer next to the cold plate 152, the armature windings156 may traverse the gap 202 transversally in the reverse of they-direction of the traversal on the outermost layer. The pattern of thestaggered and stepped armature windings 156 for the three phases may berepeated along the cores 154 of the motor in the x-direction. FIG. 14shows one embodiment of the stepped armature windings 156 in which thepole pitch is ⅔ of the slot width.

Referring back to FIG. 2 that shows a perspective view of the steppedarmature windings 156 and the cores 154 from above the motor along thex-direction. The advantages of the stepped armature windings 156 areshort end windings, symmetric inductance, and elimination of secondorder force ripple.

While the specification describes particular embodiments of the presentdisclosure, the description is not intended to be exhaustive or to limitthe invention to the precise forms disclosed. Many modifications andvariations are possible in view of the above teachings. The embodimentswere chosen and described in order to best explain the principles of theinvention and its practical applications. They thereby enable othersskilled in the art to best utilize the invention and various embodimentswith various modifications as are suited to the particular usecontemplated. Those of ordinary skill can devise variations of thepresent disclosure without departing from the inventive concept.

What is claimed is:
 1. A machine having a moving member, the movingmember comprising: a cold plate having a plurality of slots through thecold plate; a plurality of ferromagnetic cores coupled to the coldplate, each of the plurality of ferromagnetic cores protruding through arespective one of the plurality of slots, creating gaps between theplurality of ferromagnetic cores; and a plurality of armature windingscoupled to the cold plate, the plurality of armature windings occupyingthe gaps between the plurality of ferromagnetic cores, wherein each ofthe plurality of armature windings is configured to step through aplurality of levels in a vertical direction from a face of the pluralityof ferromagnetic cores.
 2. The machine of claim 1, wherein magnetic fluxgenerated by a pole pair of the plurality of armature windings flowthrough one or more of the plurality of ferromagnetic cores.
 3. Themachine of claim 1, wherein the plurality of ferromagnetic cores isconstructed of silicon steel.
 4. The machine of claim 1, wherein theplurality of ferromagnetic cores are constructed from a plurality ofsheets of ferromagnetic materials laminated together.
 5. The machine ofclaim 1, wherein each of the plurality of armature windings is woundaround one of the plurality of ferromagnetic cores.
 6. The machine ofclaim 1, wherein each of the plurality of armature windings carries oneof three phases of an alternating current, and wherein a group of threeof the armature windings carrying the three phases are respectivelywound around three successive ones of the plurality of ferromagneticcores.
 7. The machine of claim 6, wherein a pole pitch of the pluralityof armature windings is less than a width of a track, and whereinmagnetic flux generated by a pole pair of the plurality of armaturewindings flows to the track through an air gap between one or more ofthe plurality of ferromagnetic cores and the track.
 8. The machine ofclaim 7, wherein the track is part of a stator of a linear motor.
 9. Themachine of claim 1, wherein each of the plurality of armature windingsis wound around two of the plurality of ferromagnetic cores, wherein thetwo ferromagnetic cores are separated by one or more of the gaps betweenthe plurality of ferromagnetic cores.
 10. The machine of claim 1,wherein each of the plurality of armature windings carries one of threephases of an alternating current, and wherein the armature windingscarrying the three phases are stacked along a vertical direction of theplurality of ferromagnetic cores.
 11. The machine of claim 10, whereinthe armature windings carrying a same phase are stacked to havesubstantially a same distance in the vertical direction from a face ofthe plurality of ferromagnetic cores.
 12. The machine of claim 10,wherein the armature windings carrying the three phases are staggeredalong a longitudinal direction of the plurality of ferromagnetic coresso that portions of the armature windings carrying the three phasesoverlap.
 13. The machine of claim 10, wherein the armature windingscarrying the three phases are stacked along the vertical direction ofthe plurality of ferromagnetic cores protruding through the plurality ofslots on both sides of the cold plate.
 14. The machine of claim 1,wherein the plurality of levels in the vertical direction comprisesthree levels, and wherein each of the plurality of armature windings isconfigured to step to a successive level of the three levels whentraversing a successive one of the plurality of gaps along alongitudinal direction of the plurality of ferromagnetic cores.
 15. Themachine of claim 1, wherein each of the plurality of armature windingscarries one of three phases of an alternating current, and wherein thearmature windings carrying the three phases are staggered along alongitudinal direction of the plurality of ferromagnetic cores so thatportions of the armature windings carrying the three phases overlap. 16.The machine of claim 1, wherein the plurality of armature windings arepart of a rotor of a linear motor.
 17. A system, comprising: a statorconfigured to have a plurality of c-channel segments that includeferromagnetic material; and a mover, comprising: a cold plate having aplurality of slots through the cold plate; a plurality of ferromagneticcores coupled to the cold plate, each of the plurality of ferromagneticcores protruding through a respective one of the plurality of slots,creating gaps between the plurality of ferromagnetic cores; a pluralityof armature windings coupled to the cold plate, the plurality ofarmature windings occupying the gaps between the plurality offerromagnetic cores; and one or more field windings fixed to the coldplate, wherein the mover is propelled through the c-channel segments bymagnetic force generated by the plurality of armature windings and theone or more field windings.
 18. The system of claim 17, wherein magneticflux generated by a pole pair of the plurality of armature windings flowthrough one or more of the plurality of ferromagnetic cores.
 19. Thesystem of claim 17, wherein the plurality of ferromagnetic cores isconstructed of silicon steel.